I did tip an auto mechanic once. I was changing shocks on a minivan. I compressed the coil spring to get everything apart, but then lost confidence in the spring not killing me. Took the parts to the shop in a paper bag with my diy story. They obviously had a better spring compressor and did it lickity split. They charged me $20. I insisted they take $40. They said they admired me for knowing my limitations and seeking help.
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